BTP

BTP is a format used to store animations involving texture swaps. It is mainly used in The Wind Waker for animating characters' facial expressions. It consists of the standard animation header, followed by the TTP1 chunk, which stores information unique to the BTP format.

Keyframe Data

Each material being animated has one keyframe entry. The format for keyframes is shown below.

// 8 bytes long
/*0x00*/ short FrameCount; // Number of frames in the anim
/*0x02*/ short FirstIndexOffset; // Index of the first texture index in the texture index bank
/*0x04*/ short Unknown1; // Always 0x00FF?
/*0x06*/ short Unknown2; // Always 0xFFFF?